L-753,037 (BQ-4508-2) is a potent selective antagonist of ETa and ETb receptors. It shows antihypertensive efficacy in several rodent models of hypertension including low renin models where ACE inhibitors are inactive. This multicenter, randomized, double-blind, placebo-controlled, multiple-dose study is designed to evaluate the safety, tolerability, and antihypertensive activity of a 1 mg daily dose of L-753,037 in African-American patients with mild-to-moderate hypertension.